Assessment of fetal corpus callosum biometry by 3D super-resolution reconstructed T2-weighted magnetic resonance imaging

Abstract

Objective: To assess the accuracy of corpus callosum (CC) biometry, including sub-segments, using 3D super-resolution fetal brain MRI (SR) compared to 2D or 3D ultrasound (US) and clinical low-resolution T2-weighted MRI (T2WS).

Method: Fetal brain biometry was conducted by two observers on 57 subjects [21-35 weeks of gestational age (GA)], including 11 cases of partial CC agenesis. Measures were performed by a junior observer (obs1) on US, T2WS and SR and by a senior neuroradiologist (obs2) on T2WS and SR. CC biometric regression with GA was established. Statistical analysis assessed agreement within and between modalities and observers.

Results: This study shows robust SR to US concordance across gestation, surpassing T2WS. In obs1, SR aligns with US, except for genu and CC length (CCL), enhancing splenium visibility. In obs2, SR closely corresponds to US, differing in rostrum and CCL. The anterior CC (rostrum and genu) exhibits higher variability. SR's regression aligns better with literature (US) for CCL, splenium and body than T2WS. SR is the method with the least missing values.

Conclusion: SR yields CC biometry akin to US (excluding anterior CC). Thanks to superior 3D visualization and better through plane spatial resolution, SR allows to perform CC biometry more frequently than T2WS.

Keywords: agenesis of the corpus callosum; biometry; corpus callosum; corpus callosum segments; fetal brain; magnetic resonance imaging; super-resolution reconstruction; ultrasound.

Figure 1

Data selection flow chart.

Figure 2

Corpus Callosum Imaging: (A) Imaging approaches: 3D ultrasound (top), T2WS MRI (middle, sagittal acquisition reoriented view for clarity; low- resolution T2WS also in coronal and axial orientations), 3D super-resolution (SR) reconstructed MRI (bottom); (B) CC and sub-segment biometry (from anterior to posterior: rostrum, genu, body, splenium) and manual CC area delineation (bottom).

Figure 3

Imaging quality and availability of measurements: CCL was measured 100% in all modalities; the percentage of measurements per imaging method (US/T2WS/SR) are, respectively, 72/82/96 for rostrum, 86/96/100 for genu, 86/100/100 for body and 81/98/100 for splenium.

Figure 4

(A) Corpus callosum length and heights by obs1. Pathological subjects with partial CCA are shown (illustrated by triangles) but not used for the regression curves. First column: Length of the corpus callosum: (B) US and T2WS measurements are, respectively, compared with previous reported values in the literature (gray solid and dashed lines) from US (36) and T2WS MRI (37). Please note that no literature values exist for CCL on SR. Columns 2 to 5: CC heights: previous reported values (36) (solid and dashed lines) from US measurements are overlayed for all three image modalities.

Figure 5

Bland–Altman plots for CCL and CC heights assessing expert US vs. expert MRI measurements (T2WS in blue, SR in yellow) for all normal (cross symbol) and pathological subjects (triangle symbol) with partial CCA. The plot’s x-axis shows the average measurement, while the y-axis shows the difference in measurements between them. The average difference in measurements is represented by the solid line, while the 95 percent confidence interval limits are represented by the dashed lines. Dashed lines = 95% limits of agreement, and shadow areas correspond to the 95% confidence interval (CI).

Figure 6

Area of CC with GA: manual delineation on US, T2WS and SR. Pathological subjects with partial CCA are shown (illustrated by triangles) but not used for the regression curves.